QEMU/KVM Panic on USB Mount
spawk at acm.poly.edu
Sat Jul 10 02:27:56 UTC 2010
Hans Petter Selasky wrote:
> On Friday 09 July 2010 19:12:59 Sean Bruno wrote:
>> In order to come up with the most convoluted problem possible, I present
>> to you screen shots of a panic from a FreeBSD VM running in QEMU
>> emulation under RedHat's KVM infrastructure.
>> I presented a perfectly functional USB partition from my host machine to
>> the VM. Then I attempted to mount the partition from FreeBSD and it
>> generated the panics located here:
>> This is 100% reproducible. But not an emergency or anything.
> It might be that there is a conflict that both the VM and the OS is accessing
> / loading drivers on the same USB device. The panic seems not directly related
> to USB.
I followed the code for a while and the cause of the panic appears to be
that ffs_vgetf() in /usr/src/sys/ufs/ffs/ffs_vfsops.c fails in one of
the several ways possible, causing in VFS_ROOT() in
/usr/src/sys/kern/vfs_mount.c to return a non-zero value and resulting
in the panic. I think the problem calls for someone with serious VFS chops.
The I/O errors from the USB device are suspicious (in that they may
cause the mount code to misbehave if they occur during its course).
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